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  • Simon Collins

River Mole August Health Report!

Our August River Mole River Watch test result are in! Our fantastic citizen scientists were out collecting data across the entire catchment last weekend. Sadly the results show some of the worst phosphate pollution levels so far with the highest catchment average phosphate level yet recorded.

More tributaries than ever also scored off-scale 2.50ppm which indicates a BAD water quality status, the lowest status possible indicating a major impact on ecological health.

The average phosphate level for the whole catchment rose to 1.24ppm which is the highest recorded so far since we started testing in May. This means the catchment as a whole falls into the POOR water quality status (WQS).

Overall, phosphate levels continued to be highest in the "middle" reaches of the Mole, south of the Stepping Stones at Box Hill, with a mean test result of 1.34ppm. However, the Lower Mole average, that is the area north of the Mole Gap, was highest of the four months at 1.11ppm. The upper reaches of the Mole at Bewbush Brook, Baldhorns Brook and Gatwick Stream (upstream section) returned some Good WQS.

Three streams recorded notable increases in phosphate level, and declining status, including Redhill Brook, Hookwood Common Brook, Burstow Stream and Salford Streams. These streams all joined Leigh Brook with off-scale levels >2.5 ppm showing BAD WQS. Leigh Brook continues to be by far the worst performing water course in the catchment with a consistent run of Bad WQS. Burstow Stream also scored 2.5ppm, BAD WQS, downstream of the sewage works but improved markedly upstream of the treatment works at Peeks Brook with 0.21ppm a Moderate WQS. This improvement immediately upstream will be a focus for our investigations as our involvement in the Gatwick Stream improvement scheme rolls out soon in partnership with South East Rivers Trust.

More happily, four streams recorded GOOD WQS. Shag Brook, flowing off Reigate Heath, retains the highest water quality in the catchment with tests showing HIGH WQS throughout the Summer. Unfortunately, August tests show poor WQS for the brook flowing through Betchworth which is immediately adjacent to Shag Brook.

While some streams showed a marked increase in phosphate level in August, a few did show some improvement such as Bewbush Brook flowing through south west Crawley and Wallace Brook flowing out of Reigate.

Overall the River Mole catchment appears to reflect the national picture which is that 14% of water courses achieve good or better water quality status.

Our citizen scientists monitor numerous aspects of river health. Here are some frequently occurring observations they made from the August round of visits to their adopted stretch of river.

Our fabulous citizen scientists range from the young to the youthful and all were out last weekend testing across the River Mole catchment. There is a lot more analysis to do on these results particularly as more months build up. We are not yet able to identify causes or sources of pollution but the data will inform further investigations and build a picture of river health to focus out resources. Thank you again to our wonderful citizen scientists who work so reliably to collect the data each month. Please support out work using the donate button and subscribe to this blog for more news and updates on our precious local river.

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